1. Field of the Invention
This invention relates to the use of terminally blocked alkyl polyethyleneglycol ethers as co-collectors in the flotation of non-sulfidic ores together with anion-active surfactant components, and to a process for the separation of non-sulfidic ores by flotation.
2. Statement of Related Art
Flotation is a separation technique commonly used in the dressing of mineral ores for separating valuable minerals from the gangue. Non-sulfidic minerals in the context of the present invention are, for example, apatite, fluorite, scheelite, baryta, iron oxides and other metal oxides, for example the oxides of titanium and zirconium, and also certain silicates and aluminosilicates. In dressing processes based on flotation, the ore is normally first subjected to preliminary size-reduction, dry-ground, but preferably wet-ground, and suspended in water. Collectors or collector mixtures are then normally added, often in conjunction with frothers and, optionally, other auxiliary reagents such as regulators, depressors (deactivators) and/or activators, in order to facilitate separation of the valuable minerals from the unwanted gangue constituents of the ore in the subsequent flotation process. These reagents are normally allowed to act on the finely ground ore for a certain time (conditioning) before air is blown into the suspension (flotation) to produce a froth at its surface. The collector acts as a hydrophobicizing agent on the surface of the minerals causing the minerals to adhere to the gas bubbles formed during the aeration step. The mineral constituents are selectively hydrophobicized so that the unwanted consituents of the ore do not adhere to the gas bubbles. The mineral-containing froth is stripped off and further processed. The object of flotation is to recover the valuable material of the ores in as high a yield as possible while at the same time obtaining a high enrichment level of the valuable mineral.
Surfactants and, in particular, anionic and cationic surfactants are used in the flotation-based dressing of ores. Known anionic collectors are, for example, saturated or unsaturated fatty acids, alkyl sulfates, alkylether sulfates, alkyl sulfosuccinates, alkyl sulfosuccinamides, alkyl benzene sulfonates, alkyl sulfonates, petroleum sulfonates, acyl lactylates, alkyl phosphates, and alkyl ether phosphates.
In contrast to anionic and cationic surfactants, nonionic surfactants are hardly ever used as collectors in flotation. In Trans. Inst. Met. Min. Sect. C 84 (1975), pages 34 to 39, A. Doren, D. Vargas and J. Goldfarb report on flotation tests on quartz, cassiterite and chrysocolla which were carried out with an adduct of 9 to 10 moles ethylene oxide with octylphenol as collector. Combinations of ionic and nonionic surfactants are also occasionally described as collectors in the relevant literature. Thus, A. Doren, A. van Lierde and J. A. de Cuyper report in Dev. Min. Proc. 2 (1979), pp. 86-109 on flotation tests carried out on a non-sulfidic tin ore with a combination of an adduct of 9 to 10 moles ethylene oxide with octylphenol and an octadecyl sulfosuccinate. In A. M. Gaudin Memorial Volume, edited by M. C. Fuerstenau, AIME, New York, 1976, Vol. 1, pp. 597-620, V. M. Lovell describes flotation tests carried out on an apatite with a combination of tall oil fatty acid and nonylphenol tetraglycol ether.
Published German patent application No. 35 17 154.5 (U.S. pending application Ser. No. 861,672, filed May 11, 1985) proposes the use of nonionic ethylene oxide/propylene oxide adducts in addition to anionic, cationic or ampholytic surfactants as aids in the flotation of non-sulfidic ores.
In many instances, the anionic and ampholytic collectors used for flotation do not lead to satisfactory recovery of the valuable minerals when used in economically reasonable quantities.